Luminous tube system



\ June 19, 19.134. 1,963,366

LUMINOUS TUBE SYSTEM Filed June 28, 1930 17 1 23 C l: [Fl 3 Q A IN V EN TOR. 6:026: 27 /7 BY 33 A WW Patented June 19, 1934 UNITED STATES PATENT OFFICE.

Claims.

This invention relates to luminous tube systems and more particularly to protective devices for use in such systems.

In luminous tube systems utilizing tubes hav- 5 ing a gaseous filling of neon, argon, helium and the like failure of one or more tubes to function sometimes occurs in spite of all precautions which may be taken to avoid it. Such a failure may be caused by leakage of the gaseous filling, occlusion of the gas by the walls and electrodes of the tube or defects in the construction of the tube itself. Frequently,'a number of tubes are connected in series in the same circuit and fail ure of one of the tubes disables all of the others. Generally, tubes of this character are connected to the output of a step-up transformer and when failure of one of the tubes occurs, the circuit of the secondary winding is opened and resulting leakage of the high potential current may result in injury to the transformer or may be the cause of a fire in the premises where it is located.

It is one object of this invention to provide means in a luminous tube system for reestablishing a circuit which has been broken by failure of one of the tubes.

Another object is to provide a protective de vice in a system utilizing luminous tubes.

Still another object is to provide means for shunting a defective tube in a system of this character whereby energization of the other tubes in the same series circuit is continued.

Other objects and advantages will become ap parent to those skilled in the art as the detailed description of one embodiment of my invention proceeds.

Attention is directed to the accompanying drawing in which:

Fig. 1 is an elevational view of a luminous tube sign embodying the principles of this invention.

Fig. 2 is a plan view of the sign shown in Fig. 1.

Fig. 3 is a view in detail of my novel protective device or cut-out.

Briefly, the invention resides in a protective device or cut-out which is adapted to be connected in an electrical circuit in parallel with a luminous tube. Preferably the protective device comprises a gas filled tube having a certain definite breakdown potential which is somewhat greater than the breakdown potential of the tube which it shunts. Normally, the current takes the path through the luminous tube since this path has less resistance. Upon failure of one of the tubes, however, the resistance of the de fective tube becomes greater and the current then flows through the protective device. On account of the high voltage and the small current ordinarily employed in systems of this type, the increase in resistance does not materially affect the circuit. The load in the output of the transformer is thus maintained and when a number of tubes are connected in series, the operative tubes continue to function as before.

Referring to the drawing I have shown a luminous tube sign comprising a background member 16 having mounted on the front side thereof a plurality of luminous tubes 1'7 and 18. Tubes 17 and 18 are filled with a conducting gas such as neon, helium, or the like and are adapted to become luminous when a high potential is impressed across their terminals. When employed in a sign, these tubes usually have a symbolic configuration to represent letters, numerals or pictures and I have illustrated tubes 1'! and 18 as forming the letters S and N.

For energizing tubes 17 and 18 a suitable transformer 19 is employed having a primary winding 21 and a secondary winding 22. The energizing circuit for the tubes may be traced from secondary winding 22, through line 23, to terminal 24 of tube 17, through tube 17, terminal 26, line 27, terminal 28, through tube 18, terminal 29 and line 31 back to the secondary winding 22. Connected across the terminals 24 and 26 of tube 17 is my novel cut-out device, such as 32 and 33.

Each cut-out tube comprises a non-conducting sealed tube 34, preferably of glass, having a filling of inert conducting gas, such as argon or helium. Lead-in wires 36 and 37, preferably formed of conducting material having approximately the same coefilcient of expansion as glass, are sealed in the tube and extend into the interior. An electrode 38 of conducting material capable of withstanding high temperatures, such as tungsten, is mounted on the end of lead-in wire 36 and a similar electrode is mounted on the end of lead-in wire 37. A high potential current impressed across the terminals 36 and 37 of the device is adapted to jump across the gap between electrodes 38 and 39 and sustain a glow discharge.

The construction and dimensions of the cutout device are preferably such that it has a greater breakdown potential than the luminous tube with which it is connected in shunt. In using luminous tubes having a filling of neon of 10 to 12 mm. pressure, I have found that a cut-out device having a filling of argon of 400 to 700 mm. pressure and a gap between its electrodes of approximately one-quarter of an inch operates very satisfactorily. Under these conditions each cut-out device has a greater breakdown potential than its associated luminous tube and the current, therefore, flows through the luminous tubes in series with little or no current passing through the cut-out devices. Upon failure of one of the tubes, such as tube 17, due to defects occurring in the tube, its resistance becomes considerably higher and it will exceed the resistance of the cut-out device 32 connected in shunt with the tube. Under these conditions the current in the circuit is shunted around the defective tube through the cut-out device connected across its terminals. Other tubes, such as tube 18, which are still operative are energized as before and continue to function. Thus, the operative tubes are not disabled by failure of one of the other tubes in the circuit.

Heretofore, failure of one of the tubes of a luminous tube system resulted in opening the circuit of the output of transformer 19. As the voltages required for the operation of luminous tubes of this character is ordinarily relatively high, frequently being in the neighborhood of 15,000 volts, there is likelihood of burning out the transformer when the secondary is opened. Furthermore, unless abundant precautions are taken, high potential current of such magnitudes will ordinarily take some other path which may result in a fire in the premises where the transformer is located. A cut-out device such as I have disclosed, therefore, serves also as a protective device since it reestablishes the circuit of the secondary winding of the transformer. In the exercise of this invention a safe path is provided for the current through cutout devices 32 and 33 instead of allowing the current to flow uncontrolled through some undesired path. For this reason it is advantageous to use such a cut-out device even when a single luminous tube is employed.

Preferably, the cut-out devices 32 and 33 are mounted in some convenient place at the rear of the sign where they are hidden from the front view, in order not to affect the appearance of thesign.

While I have shown and described a preferred embodiment of my invention, I do notwish to be limited thereto, since the invention as defined in the appended claims can be embodied in a plurality of forms.

I claim:

1. In a luminous tube system a plurality of luminous tubes connected in series and a gas discharge tube connected in shunt with each of said luminous tubes.

2. In a luminous tube system a plurality of luminous tubes connected in series and a gas discharge tube connected in shunt with each of said luminous tubes, each of said gas discharge tubes having a breakdown potential which exceeds that of its associated luminous tube.

3. In a luminous tube system, a plurality of luminous tubes connected in series and a gas discharge tube connected in shunt with each of said luminous tubes, said luminous tubes having a symbolic configuration to form a sign and said gas discharge tube being placed in inconspicuous position relative to the sign.

4. In a luminous tube system, a plurality of luminous tubes connected in series, a gas discharge tube connected in shunt with each of said luminous tubes, each of said gas discharge tubes having a breakdown potential which exceeds that of its associated luminous tube, said luminous tubes forming a sign and said gas discharge tubes being hidden from the front view of the sign thus formed.

5. In a luminous tube sign, a background member, a plurality of luminous tubes having symbolic configuration mounted on the front of said background member and connected in series in an electric circuit, and a gas discharge tube connected in shunt with each of said luminous tubes mounted on the rear of the background member.

GEORGE E. HILL. 

